A Novel Testicular Germ Cell Maturation Model for Fertility Preservation in Pre-p

描述（由申请人提供）：2005年，美国大约4%的癌症患者年龄在35岁以下（see .cancer.gov）。随着癌症治疗的显著进步，对许多人来说，生存是一个现实的结果（see .cancer.gov），最小化治疗脱靶效应的重要性已经成为患者管理的重中之重。化疗和放疗等治疗方式可对生育产生深远和不可逆转的影响。随着我们治疗方法的改进，越来越多的年轻癌症患者存活了下来，这引发了关于长期幸存者生活质量的重要问题。保存生殖能力正成为这些生活质量问题中最重要的问题之一。在即将接受癌症治疗的年轻男性中，最广泛使用的保持生育能力的策略是减少癌症治疗的毒性和配子的低温保存，以备将来的辅助生殖技术。不幸的是，青春期前的男孩不能产生成熟的精子，所以我们不能为这个群体冷冻保存精子。我们对癌症治疗对男性生育能力的影响了解有限。特别是，我们对青春期前男孩的影响的了解非常初级。几乎所有的实验室工作都使用动物模型来研究癌症治疗对生育能力的影响。将动物研究的数据外推到人类睾丸中存在明显的缺陷。此外，动物模型的研究主要集中在化疗对成熟成人睾丸的影响上。在我们的实验室里，我们开发了一个独特的人类青春期前睾丸模型，将人类胎儿睾丸移植到小鼠体内。移植的胎儿睾丸存活并发育成在组织学上与青春期前的睾丸非常相似。该模型为我们直接研究化疗药物对青春期前人类睾丸的影响提供了机会。在研究的第一部分，我们将给睾丸移植小鼠注射不同浓度的常用化疗药物环磷酰胺，研究这种化疗对人类青春期前睾丸的影响。我们项目的第二部分是用促性腺激素刺激在我们的人类睾丸异种移植模型中诱导精子发生。青春期的开始涉及一系列复杂的内分泌事件，最终以促性腺激素的增加和随后的精子生成的诱导而告终。促性腺激素水平低或缺乏的男性，如卡尔曼综合征患者，有青春期前睾丸；外源性促性腺激素可以成功地诱导精子发生。在这个项目中，我们打算使用类似的策略，在我们的人类睾丸异种移植模型中使用外源性促性腺激素来刺激精子发生。如果成功，这将是人类生殖细胞在体外成熟的首次报道。这个项目的主要优势是我们建立的人类胎儿睾丸异种移植模型。这个模型是一个独特而强大的系统，它使我们能够直接探索癌症治疗对青春期前睾丸的影响，并开始了解如何减少或预防毒性。我们还建议在该人类睾丸模型中使用不同的策略诱导精子发生，以产生成熟的人类睾丸模型。这对于任何生殖毒理学研究来说都是一个非常强大的系统，但也会让我们了解成熟青春期前睾丸的技术，这些信息对接受癌症治疗的青春期前男孩的生育能力保持至关重要。

DESCRIPTION (provided by applicant): In 2005, approximately 4% of cancer patients were under the age of 35 in the United States (seer.cancer.gov). With the remarkable advances in cancer therapy, survival is a realistic outcome for many (seer.cancer.gov) and the importance of minimizing off-target effects of therapy has come to the forefront in patient management. Treatment modalities such as chemotherapy and radiotherapy can have a profound and irreversible impact on fertility. As our therapies improve, an increasing number of young cancer patients survive, leading to important questions about the quality of life of the long term survivors. Preservation of reproductive ability is becoming one of the most important of these quality of life issues. The most widely used strategies to preserve fertility in young men about to undergo cancer therapy are to reduce the toxicity of the cancer therapies and cryopreservation of gametes for future assisted reproductive technology. Unfortunately, pre-pubertal boys do not produce mature sperm, so we do not have the option to cryopreserve sperm for this group. We have limited knowledge about the effects of cancer therapy on male fertility. In particular, our knowledge about the effects on pre-pubertal boys is very rudimentary. Virtually all of the laboratory work has used animal models to study the effects of cancer therapy on fertility. There are obvious pitfalls in extrapolating data from animal studies to human testis. In addition, studies on animal models have concentrated on the effects of chemotherapy on mature adult testis. In our laboratory, we have developed a unique human pre-pubertal testis model using human fetal testis transplanted into mice. The transplanted fetal testis survives and develops to become histologically very similar to pre-pubertal testis. This model provides us with the opportunity to directly study the effects of chemotherapeutic agents on pre-pubertal human testes. For the first part of the study, we will administer different concentrations of the commonly used chemotherapy agent, cyclophosphamide, to the mice with the testis transplant to study the effects of this chemotherapy on human pre-pubertal testis. The second part of our project is to induce spermatogenesis in our human testis xenotransplantation model with gonadotropin stimulation. The initiation of puberty involves a series of complex endocrine events culminating in an increase in gonadotropins and the subsequent induction of spermatogenesis. In men with low/absent gonadotropins, such as in Kallman's syndrome, have pre-pubertal testis; exogenous gonadotropins can successfully induce spermatogenesis. In this project, we intend to use a similar strategy by using exogenous gonadotropins to stimulate spermatogenesis in our human testis xenotransplantation model. If successful, this will be the first report of human germ cell maturation outside the human body. The major strength of this project is our established human fetal testis xenotransplantation model. This model is a unique and powerful system which allows us to directly probe the effects of cancer therapies on pre- pubertal testis and begin to understand how toxicity may be reduced or prevented. We also propose to use different strategies to induce spermatogenesis in this human testis model to produce a mature human testis model. This would again be an extremely powerful system for any studies on reproductive toxicology, but would also give us insights into techniques to mature pre-pubertal testis, information which will be critical to the fertility preservation of pre-pubertal boys having cancer therapy. PUBLIC HEALTH RELEVANCE: Our goals for this project are twofold: (1) Validate our human testis xenotransplantation model as a useful tool to study the toxic effect(s) of commonly used cancer chemotherapeutic agents on human testis and (2) hormonally stimulate per-pubertal human testis to develop towards mature sperm in our robust xenotransplantation model. If successful, we will have a direct method to evaluate the impact of any gonadotoxic agent, explore opportunities to minimize their harmful effects on human fertility, and develop the first human-mouse xenotransplant system to restore fertility in the human pre-pubescent population. vcolin 14 October 2009